Some are children of God, some are not.
1 John 3: 10 says: In this the children of God are manifest, and the children of the devil: whosoever does not righteousness is not of God, neither he that loves not his brother.
Romans 3: 22 explains how to "do" righteousness: even the righteousness of God, through faith in Jesus Christ, to all and on all who believe. For there is no difference;
There is NOW (since Calvary) no difference between Jew and Gentile.
I noticed that you are still using the NWT.
In Acts 17; 20-28, the greek word Fred Franz translated as "children" in these NWT verses is genos. It is better translated as "offspring" and not children... since it denotes we are all of the same geno-type or species.
For in him we live, and move, and have our being; as certain also of your own poets have said, For we are also his offspring. Forasmuch then as we are the offspring of God, we ought not to think that the Godhead is like unto gold, or silver, or stone, graven by art and man's device. - KJV
In 1 John 3: 10 I cited above in the 1st paragraph, the greek word for children is teknon. It means a son or daughter, a family member.
None of us start out as a child of God. We are born into a state of condemnation.
John 3: 18 - He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.
This is why in a conversation with Nicodemas, Jesus 3 times says that we must be "born-again".
Family and genotypes are not the same. A person must be grafted in (adopted) to the family of faith (trust, belief) started with Abraham. This is one of the key Christian doctrines the WT seeks to hide and deny to "whosoever".